MOBILE MACHINERY “On the assembly line, it is critical whether a hydraulic line system is leak-tight in operation”, explains André Degen, application engineer with Stauff, the developer and producer of all components for hydraulic line systems based in the German town of Werdohl. When he visits machine and plant manufacturers across Europe with the Stauff-Liner, he experiences at first hand how important the straightforward and intuitive assembly of tube connectors is. And this aspect is equally important in Stauff Engineering. Stauff supplies 24° tube connectors, among others, to connect hydraulic tubes with outside diameters of 6 to 42 mm, which are Maintenance and repair work is generally also done at the place of use, for instance on site. Not having to forego the benefits of mechanical pre-assembly reduces the risk of assembly errors and helps to reliably prevent leaks – regardless of the installation site. André Degen, application engineer at Stauff, Werdohl O+P Fluidtechnik 2024/07-08 www.oup-fluidtechnik.de based on a cutting ring with two cutting edges arranged in tandem. Alongside its pure metallic cutting rings, Stauff also supplies the FI-WDDS range with two FKM (Viton®) soft seals positioned to remain in place. The first part of the assembly process involves fixing the cutting ring on the prepared tube, so-called pre-assembly. When the union nut is tightened, the two edges of the ring cut into the tube, one after the other, plastically deforming it and producing a force fit and form fit with excellent tear-out strength. The raised material clearly visible on all sides in front of the contact face signals the end of manual pre-assembly to the user and acts as tear-off resistance. FROM MANUAL FITTINGS TO MECHANICAL ASSEMBLY There are various aids available for pre-assembly, from simple fittings clamped into the vice, to mechanical pre-assembly or 100% final assembly. Users choose the option that makes most sense for them. “Working together with our customers is perfect when commercial, logistics and technical advice go hand in hand. Application engineers are the interface, as it were,” continues André Degen, explaining his work. „The question of the angle of rotation is a decisive parameter in cutting ring assembly. To what percentage is the cutting ring cut into during pre-assembly, and what percentage of the tightening path still needs to be applied in the final assembly of the connector, that is when it is in use?“ Pure manual pre-assembly using a manual fitting works with an angle of rotation of 270° (3/4 of a revolution) once the pressure point has been reached (clearly perceptible increase in force) so that a further 90° needs to be applied – again once the pressure point has been reached. Old and outdated assembly strategies by different manufacturers allowed for pre-assembly angles of rotation of only 50%, which then required twice the angle of rotation during final assembly and so did not achieve the pre-assembly result required according to DIN 3859-2. “This can be difficult in many installation situations, whether in tight spaces or with overhead fittings. Generally the assembly wrench has to be moved multiple times. This takes extra time, which is already comparatively lengthy with manual assembly, but can be justified with smaller numbers where no major investment is needed in pre-assembly.” The entire tightening process is done using a conventional face spanner. And the union nut used is also a traditional DIN product. 01 02
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